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DailySWE_Rasters folder
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"DailySWE_Rasters" folder contains netcdf (.nc) versions of the SNODAS SWE rasters  for all March through August dates each year from 2004-2021 (Febraury days also included for some years). From these rasters, SWE and Snow-covered area metrics were extracted for the persistent snow zone, and formed the bases for the snowpack analysis in the research manuscript. The daily-level extracted values can be found in the "PersistentSnowZone_DailySnow+Temp_Data.csv".
These rasters were used for the spatial data figures in Fig 2b-d.

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"PersistentSnowZone_DailySnow+Temp_Data.csv" is the master spreadsheet of all extracted values at the daily level, days from March to August, in the period 03/1981-08/2021. This data formed the basis for most figures, including the time series plots (Fig 2a, Ex Data Figs 2-4), bar plot (Ex Data Fig 1), scatterplots (Fig 3, Ex Data Fig 5), and the heatwave summary in Ex Data Table 2.
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SNODASValidation folder
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Data in this folder forms the basis for the data shown in the Supplementary Data file (tables and figures) as well as any reference to this data in the main manuscript.

"RawObservations" folder contains spreadsheets of the raw observations of snow depth from 28 stations, generally by year, of the stations used in our SNODAS validation effort. These spreadsheets also contain the corrected values where any post-processing data correction was applied. These values were imported from the native datalogger file formats (generally .dat), and represent a SNODAS-independent observational dataset compiled from NW Avalanche Center, National Park Service, and Western Regional Climate Center stations in the Western US.

"StationsShapefile" contains a shapefile of the point locations of the stations.

"StationDailyData" is a csv of all observed (stations) and modeled (SNODAS) snow depth data, for all stations and years in the validation effort (09/2003-09/2012).

"StationMetrics" contains the observed vs modeled comparison for points of comparison: Peak Snow Depth as found using a 15-day moving average, the Date of that Peak Snow Depth, and April 1st snow depth. The column "DistanceResult" identifies each station as one to "keep" or "drop" from the regression analysis that tested for an effect from spatial autocorrelation by dropping stations that were within 10km of each other.

"StationDistanceMatrix" is a distance matrix of the (Haversine) distance (in meters) between all combinations of station in the validation effort.

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StationTemperatureRecords folder
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Files are either the Daily Temperature observations at a station (GHCNStationNameHistoricalDailyStartYearEndYear), or a summary file (*5Cbyyr.csv) that summarizes, by year, different temperature metrics during the April-May-June (AMJ) period each year. The summary file was generated by going through the historical daily record and compiling the metrics of interest for each year.
The metrics are:
*StationInitials*DegDayPlus5C_30 - the metric plotted in the manuscript figures and referenced principally therein, the temperature anomaly (in C) of all days from April 1 - June 30 each year where there was an anomaly > +5C.
*StationInitials*DayCountPlus5C_30 - for the same AMJ period, the number of AMJ days each year with an anomaly > +5C.
*StationInitials*DegExpOver5C_30 - for the same AMJ period, for all days with at least a +5C anomaly, how much each anomaly exceeded 5C, summed across all days in each year's AMJ period.
These metrics are related in that:
DegDayPlus5C_30 = (DayCountPlus5C_30 x 5) + DegExpOver5C_30

The summary files are the basis for the Temperature trend plots (Figure 4a-b, Extended Data Fig 6a-d) as well as Extended Data Table 1. The Station name USGHCN identifiers are as follows:
Forks 1 E: USC00452914
Mud Mountain Dam: USC00455704
Wickiup Dam: USC00359316
Medford International Airport: USW00024225
Portland International Airport: USW00024229

The PRISMZPSC5Cbyyr file is not generated from historical data, rather extracted from the summary raster of +5C AMJ anomalies for each year using the persistent snow zone shapefile, then summarized into this PRISMZPSC5Cbyyr.csv file.

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TemperatureRasters folder
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"DailyTempRasters_1981-2021" folder contains netcdf (.nc) versions of PRISM daily-scale mean temperature rasters from March-August each year (1981-2021). The PRISM record begins in 1981.

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"DailyMeanTempRasters_AMJ_1991-2020ClimMean" folder contains 30-year average mean temperature rasters for all 91 days of April, May, and June. These were generated by averaging the rasters for each date in the "DailyTempRasters_1981-2021" folder from 1991-2020, to create a 30-year average raster for each date. Each of these rasters was further smoothed using a 7-day moving average (e.g., "wnw_0415_tmean7ma.nc" was generated by averaging the 30-year average for April 15th with the 30-year average rasters for April 12th-14th and 16th-18th.).

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"AnnualAMJMeanTempAnomalyRasters" contains anomaly rasters generated for the PNW. These were derived by subtracting the raster of the 30-year average for each date (from the "DailyMeanTempRasters_AMJ_1991-2020ClimMean" folder) from the daily mean temperature raster for that date ("DailyTempRasters_1981-2021" folder). The resulting anomaly rasters had all cells where anomalies were <+5 degrees C filtered out, and then the remaining raster was added to the other rasters for the AMJ period of each year to generate the sum of +5C anomalies for each year's AMJ period which are compiled here (named with +5Ctmeananom.nc).

The tau figure, Extended Data Figure 7, was generated by running a regression through a raster brick of these +5Ctmeananom.nc rasters for the 1993-2021 period.

Rasters as above, but with the daily-level anomalies <+5C NOT filtered out, are also included for completeness' sake (named with *alltmeananom.nc).

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The "TauCorrelation_1993-2021_PNW_AMJ+5CMeanTempAnom_.nc" file is the raster displayed in Extended Data Figure 7.

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The 4 files named "PNW_TMeanAnom_20210629" (with different extensions) are the raster used for Figure 1, the daily mean temperature anomaly for June 29th, 2021.

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zpsC_shapefile folder
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"zpsC_shapefile" folder contains the shapefile for the persistent snow zone used in this study.

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"Snowpack+TemperatureProcessingCode.R" is the data processing code used to analyze the data for this study. Contact Luke.reyes@wsu.edu for assitance in deciphering and application.
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